Improved Area Light Config

[Cameron-Micka]

Overview

This PR adds extra properties to the experimental AreaLight.

• Ability to make the area light face down the positive Z axis or negative Z axis.
• Checkbox to sample the cookie texture with UV 1 or UV 0 at the top.
• Adjusting the area light cookie UV calculation to better handle perpendicular surfaces.

Verification

As a reviewer, it is possible to check out this change locally by using the following
commands (substituting {PR_ID} with the ID of this pull request):

git fetch origin pull/{PR_ID}/head:name_of_local_branch

git checkout name_of_local_branch